Define "mass produced"? 10,000 frames a year, 1,000 frames a year? 500??
Of course each manufacturer had a few steel framed Mtb's in their product line, and the quality of the tubing used would have varied according to the price point each model was aimed at. Generally the lower down the range the lower the grade of tubing, usually.
As mentioned above, steel tubing hasn't advanced hugely since the 90's like aluminium and carbon fibre has, hence most modern bikes (excluding supermarket BSO's) are made from these two materials, and as such a modern steel frame is more of a niche product and hence commands a price premium.
Also as already mentioned, the geometry has a lot to do with how a frame "feels" to ride, and geo has changed a lot since the 90's, in accordance with how many people now use their Mtb's and the type of riding and terrain they ride on.
I doubt you can really compare retro steel and modern steel on the same playing field.
Of the truly mass produced 90's bikes I always rated the Orange Prestige (I'm biased) with its Tange Ultimate Superlight MTB tubing, and the Kona Explosif, the Explosif was always a good benchmark imo.
But I've been surprised by how "nicely" other, perhaps slightly lower quality (or slightly heavier weight), steel framed Mtb's can ride, the Univega was a good example of this.